Method of concentrating fibrous materials



Patented Apr. 12, 1927.

UNITED STATES SAMUEL H. DOLBEAR AND VICTOR ZACHERT, OF'SAN FRANCISCO, CALIFORNIA, A S- 1,624,163 PATENT OFFICE.

SIGNORS, BY MESNE ASSIGNMENTS, TO SELECTIVE TREATMENT COMPANY LIM- ITED, OF MONTREAL, OANADA, A CORPORATION OF QUEBEC, CANADA METHOD or CONCENTRATING FIBROUS MATERIALS,

No Drawing.

This invention relates to methods of concentrating materials having fibrous, matty, threadlike or feathery characteristics such as asbestos, particularly pertains to a new and useful method of separating asbestos from the rocky matter with which it is associated in nature.

The method of concentrating asbestos commonly employed at present involves the preliminary drying of the ore and subsequently treating it in a dry state. The present invention avoids this dry treatment.

In the dry treatment of the ore, after being dried in rotary or other dryers, 1s

ground, and the ground dry product passed through air currents, by whichmeans the fibrous asbestos is blown away from the gangue. This procedure necessitates the drying of large amounts of waste rock and 2 produces a product which may be gritty from fine dust carried with the asbestos, and creates a dusty' atmosphere in which those employed must work.

We have discovered that fibrous, matty,

threadlike or feathery substances such as asbestos, may be gasified in a liquid, thereby causing bubbles of gas to become entrained or entangled in such substances, their specific gravity being thereby overcome, making possible a separation by flotation. 1n the case of asbestos ore, such ore is first ground sufiiciently to free the rocky matter attached to the asbestos, and to bring out the fibrous characteristics of the asbestos. In other words, it is an important desideratum, in practicing this invention, that the mass be fiberized. The separation may then be effected by submitting a liquid pulp of such an ore to flotation by any of the well-known 40 methods. Thus, by bringing such a liquid pulp into contact with bubbles of air' or other gas, minute bubbles become entrained or entangled in the fibrous material present, overcoming the specific gravity, and causing such fibrous material to be buoyed upward, while the rocky matter or gangue sinks. A multiplicity of small bubbles is desirable for this purpose, and the formation of such bubbles may be aided by the intro- (notion of smallamounts of reagents such as are commonly employed in the flotation of metalliferous ores to cause emulsification of gas with liquid.

The gas may be introduced or formed in Application filed February 16, 1921. Serial No. 445,470.

any of the well-known ways, by violent agitation, vacuum, cascading, through porous mediums, by chemical reactions within the pulp orby heating or in anyother suitable manner. Frothing reagents may also be employed.

When the ebullition is gentle, and no froth is formed, it is desirabie to provide a period of relative quiescence in which the fibrous material is buoyed gently upward while the gangue matter sinks. If such gentle ebullition is accomplished by heating, or by acid reactions, an apparatus of the type described in United States Patent No. 763,662 to G. D. Delprat may be employed; whereas if violent agitation and frothing is employed an apparatus of the type described in United States Patent No. 979,85; to T. J. Hoover may be used. That many other types of apparatus may be used in the practice of this invention will be readily apparent to one skilled in the art of flotation.

In practice it is observed that the shorter fibers rise to the surface of the liquid more readily than the longer and heavier-fibers, and this fact maybe taken advantage of to secure a classification of the product according to the length of fibers. After first removing the rocky or waste matter, the fibers may be immersed in liquid and subjected to gentle ebullition to cause the shorter fibers to first rise to the surface. After removal, the ebullition may be increased slightly with the result that longer fibers will rise, and such a procedure may be repeated with such varyingintensity of ebullition and varying periods of time of ebullition as to form several classes of products by successive flotation.

When frothing is employed to separate the fiber from gangue, the fiber will rise above the pulp into the froth and may then be removed and recovered from the froth in the manner usually employed in recovering metalliferous matter from froth. After separation, and if desired, classification, the fiber may be dried by any suitable means.

It should be noted that asbestos and other substances to which this invention is applicable, possess no'natural preference for selective flotation reagents, and that the flotation of asbestos, which is a silicate, is due to the mechanical entaglement of gas bubbles.

The asbestos ore, to be floated, must be suitably ground to bring out the fibrous or feathery characteristics of the mineral. Otherwise no gas will be entrained and no flotation accomplished. The essential feature of this invention is the mechanical entanglement of gas bubbles by fibrous and similar substances, thereby overcoming the specific gravity of such substances.

Having thus described our. invention, what we claim and desire to secure by Letters Patent is- 1. In a flotation process, the steps of first submitting an aqueous pulp of fiberized asbestos to slight aeration thereby separating one product, and subsequently submitting the pulp to substantiall greater aera- 7 tion to recover a second pro not.

SAMUEL b1. DOLBEAR. VICTOR ZACHERT. 

